1. Field of the Invention
The present invention relates to a nozzle assembly, such as a nozzle assembly which is adapted to discharge a high pressure liquid as a jet, and more particularly to such a nozzle assembly which can be easily inserted into, and removed from, the discharge opening of a high pressure housing.
2. Background Art
For a number of years, apparatus has been provided for pressurizing a liquid (e.g. water) to a high pressure (e.g. 25,000 pounds per square inch or more) and discharging this water as a high velocity jet to accomplish cutting, abrading or some other operation. One of the critical components in such an apparatus is the discharge nozzle assembly. With liquid accelerating into and through the nozzle element at a very high velocity, there can be relatively rapid wear or deterioration, and this requires frequent removal of the nozzle assembly for replacement, repair or inspection periodically.
One type of nozzle assembly which has been in use for a number of years is one which employs a sapphire nozzle element which is positioned in the discharge opening of the high pressure housing, and a retaining screw which holds the nozzle in position. This retaining screw has a forward or downstream portion which threads into the near or upstream part of the opening in the housing and a rear portion of reduced diameter which, in addition to positioning the nozzle element, provides support for a polymeric seal that surrounds both the nozzle element and the rear portion of the retaining screw. The polymeric seal is initially provided as a cylindrical member which is inserted into the end opening of the high pressure housing, and fluid pressure within the chamber of the housing causes the seal to extrude forwardly into sealing engagement with the retaining screw and the housing wall which defines the discharge opening.
One of the problems with that design has been that when the assembly is removed from the opening, the screw is initially removed, but the nozzle element and the seal would remain in the opening. Then various methods would have to be used to remove the seal and the nozzle element from the opening. Another concern has been that a fully adequate seal was not always obtained.